I'm guessing most of them suffer from it when actually at sea, not just on a day-to-day basis! Apparently after seven days at sea most people get over it and "find their sea legs". I get sick even at the idea of a boat and when I lived in Germany and we took the ferry back and forth I would always have to stand outside. I've stood on a ferry deck in all kinds of weather with fellow sufferers throwing up all around me. I've yet to actually join them but I certainly feel like I'm going to for most of the trip.